It is known in the art to provide radio frequency identification (RFID) tags to persons and objects to allow identifying them. For instance, from U.S. Pat. No. 4,418,411 A, a method and an apparatus for interrogating such RFIDs is known. A stationary interrogator may interrogate a transponder fastened to the object or the living being. The transponder may obtain its energy from the transmission of the interrogator. Using this energy, the transponder may send its identification to the interrogator. Each of the transponders may carry a unique identification number. This unique identification number may be transmitted to the interrogator. The unique identification numbers allow identifying each of the transponders uniquely.
It is also known in the art to secure entries to buildings by using chip cards and chip card readers. It is possible to interrogate the chip cards of personnel at the entry to a building and to determine whether or not to grant access to the building. The chip cards may provide a unique identification number depending on the identified unique identification number read from the chip cards for each user. A security rule may be applied, which only allows entry to the building or particular areas within the building for certain individuals. These individuals may be identified by their identification cards, i.e., by their respective unique identification numbers. Entry and exit to buildings may thereby be controlled. It may also be logged which persons enter and exit which area of a building at which time. This information may, for instance, be used for updating a balance sheet of a person regarding the time present in the building.
Further, from U.S. 2001/0169583 A1, it is known to provide RFID tokens to persons. The tokens permit the persons to identify themselves within an area. It may also be possible to monitor different persons within a building, and to provide alarm signals, in case the identified persons do not act according to security rules. For instance, the presence of a person in a living room may be detected. It may also be detected that a person needing help is located in a bedroom. According to security rules, the reaction of the person in the living room may be monitored, and an alarm signal may be generated if none of a set of expected events, such as the person in the living room moving to the bedroom, is detected in a predefined interval.